The research described in this application is designed to examine the neurotransmitters and neuronal circuitry which are responsible for the state-dependent modulation of trigeminal motoneuron membrane potential activity during sleep and wakefulness. Interdisciplinary electrophysiological and iontophoretic studies are proposed, each of which relates to and complements the others. These studies, which are organized within the framework of the examination of the paradoxical phenomenon of "reticular response-reversal", entail a determination of the state-dependent activity of the interrelationships between the pontine nucleus pontis oralis, the medullary nucleus reticularis gigantocellularis and the trigeminal motor nucleus. The proposed studies will (1) provide a comprehensive description of the frequency of occurrence and a quantitative analysis of the waveform characteristics of the newly-discovered inhibitory and excitatory postsynaptic potentials that are involved in the modulation of brain stem motoneuron membrane potential activity during sleep and wakefulness, (2) generate a normative fund of information relating to the inhibitory and excitatory neurotransmitters which mediate the postsynaptic inhibition and excitation of brain stem motoneurons during these states, and (3) establish a prototypical experimental paradigm for utilizing spike- triggered averaging, intracellular recording and iontophoretic techniques to study the cellular bases of behavior in the chronic, unanesthetized, normally respiring animal.